In recent years, the number of patients with cardiac infarction, cerebral infarction or the like is increasing. These infarctions are caused by interruption of blood flow due to obstruction or stenosis of a blood vessel, which occurs by deposition of thrombi, plaques or the like on the vascular wall. In general, for treatment of a site of obstruction or stenosis in a blood vessel, percutaneous treatment by balloon angioplasty or stenting using a balloon catheter or a stent is carried out.
In treatment by balloon angioplasty, an inflatable balloon at the distal end portion of a balloon catheter is expanded at a site of obstruction or stenosis in a blood vessel to secure the intravascular lumen and to thereby maintain the blood flow. However, when a blood vessel is expanded by the balloon, thrombi or plaques deposited on the vascular wall might be unexpectedly released, and such a substance might then be carried away by blood flow to cause obstruction of a peripheral thin blood vessel, resulting in infarction.
In treatment by stenting, a stent composed of a material such as nitinol or cobalt alloy having the shape of an almost cylindrical tube or mesh sleeve is permanently or temporarily introduced to a site of stenosis in a blood vessel to secure the intravascular lumen and to thereby maintain the blood flow. However, similar to balloon angioplasty, when the stent is placed in a blood vessel, thrombi or plaques deposited on the vascular wall might be unexpectedly released, causing infarction.
An endovascular treatment aiding device to be used in combination with a treatment device such as a balloon catheter or a stent has been developed to avoid such a risk. The endovascular treatment aiding device is percutaneously placed in a site which is more peripheral than the lesion where the balloon catheter or the stent is to be placed, and used for capturing thrombi or plaques released from the vascular wall.
As such an endovascular treatment aiding device, one having a structure containing: a shaft with an outer diameter which allows the shaft to pass through the guide wire lumen of a treatment device such as a balloon catheter; and a filter fixed at the distal end portion of the shaft; has been reported. The filter has a mesh-shaped or sheet-shaped membrane composed of a polymer material on which a plurality of openings are formed, and has a shape in which the peripheral vessel side, that is, the distal side, is closed, and the central vessel side, that is, the proximal side, is open (JP 2008-35923 A).
By this, during treatment using a treatment device such as a balloon catheter, thrombi or plaques released and carried away from the vascular wall can be captured by the filter constituting a part of the endovascular treatment aiding device placed in the peripheral side, without blocking the blood flow.
When such an endovascular treatment aiding device is used, the endovascular treatment aiding device, with its filter closed, is contained in a delivery sheath, and delivered to the site where the device is to be placed, which is located more peripheral than the lesion. After delivery, the filter is released by removal of the delivery sheath to the outside of the body. This causes self-expansion of the opening section of the filter, thereby allowing close contact of the opening section to the vascular wall. When the endovascular treatment aiding device is to be retrieved, a retrieval sheath is delivered along the endovascular treatment aiding device, and the filter containing thrombi or plaques is stored inside the retrieval sheath, followed by its removal to the outside of the body.
As an endovascular treatment aiding device that enables reduction of leakage of thrombi, plaques or the like by increasing adhesion to the vascular wall, an endovascular treatment aiding device comprising a ring-shaped member formed with a superelastic metal provided in the opening section of the filter, wherein, when the opening section of the filter is closed by bundling of the support member supporting the filter, the superelastic metal is transformed to allow folding of the filter into a bag shape, has been reported (JP 4073869 B).
An endovascular treatment aiding device comprising a coil made of a radio-opaque material arranged on a ring-shaped filter opening section, which enables observation under radiation, has been reported for the purpose of easily allowing observation of whether the filter is in close contact with the vascular wall during the operation, and whether the opening section of the filter was securely closed upon retrieval of the device (JP 4680201 B).
When such an endovascular treatment aiding device is placed in a blood vessel, the living body recognizes it as a foreign substance, and blood coagulation reaction proceeds to cause formation of a thrombus. Therefore, antithrombogenicity is required for the device. In view of this, endovascular treatment aiding devices to which antithrombogenic compounds are given have been reported (WO 2003/084437, WO 2008/005898 and WO 2013/059069).
However, in the endovascular treatment aiding device described in JP 2008-35923 A, contact with the stent may occur during delivery of a retrieval sheath because of the thick diameter of the distal end of the retrieval sheath so that there is a possibility that the retrieval sheath cannot be delivered to the filter. Moreover, since the opening section of the filter does not have a ring shape, its adhesion to the vascular wall is insufficient so that there is a possibility of leakage of thrombi, plaques or the like during treatment using a balloon catheter or the like.
In the endovascular treatment aiding device described in JP 4073869 B, the superelastic metal used for the ring-shaped filter opening section lacks radio-opaque properties so that observation by radiation transmission during the ordinary operation is impossible. Thus, there is a possibility that whether or not the device is securely adhering to the vascular wall, or whether or not the opening section of the filter has been securely closed upon retrieval of the device, cannot be known.
In the endovascular treatment aiding device described in JP 4680201 B, the superelasticity of the ring-shaped filter opening section is lost in the place where the coil formed with a radio-opaque material is arranged. Thus, the ring-shaped filter opening section cannot be appropriately transformed. Hence its secure adhesion to the vascular wall is impossible so that there is a possibility of leakage of thrombi, plaques or the like. Although the document also describes partial arrangement of the coil formed with a radio-opaque material, there is no description on a specific arrangement with which the decrease in the adhesion to the vascular wall can be prevented.
Although WO 2003/084437, WO 2008/005898 and WO 2013/059069 describe giving of antithrombogenic compounds to endovascular treatment aiding devices, there is no description on the optimal types and combinations of the antithrombogenic compounds.
That is, conventionally, there is no known endovascular treatment aiding device that solves both of the two problems, that is, there is no known endovascular treatment aiding device that allows confirmation of its secure adhesion to a blood vessel, and also allows prevention of leakage of a substance such as thrombi or plaques captured.
It could therefore be helpful to provide an endovascular treatment aiding device that allows confirmation of its secure adhesion to a blood vessel, and also allows prevention of leakage of substances such as plaques captured.